Emerging Diseases - University of Georgia College of Veterinary ...

of dollars annually. Virulence traits of thebacterial organisms that cause this disease areencoded by specific genes. These virulencespecificgenes are located either on thebacterial chromosome or large molecularweight plasmids. Escherichia coli strain V-1is a well-characterized, pathogenic avian strainisolated from a broiler chicken withcolisepticemia, and it contains severalplasmids. Two of these plasmids are highmolecular weight plasmids. The highmolecular weight plasmid, pWT3, has beencharacterized via restriction enzyme mappingand sequence analysis. This plasmid containsF-plasmid and transposon sequences,sequences encoding for (B and D) colicinproduction, virulence plasmid genes similar tothose of several species of bacteria, andresistance to several antibiotics and arsenite.We are looking for a genetic marker(designated epv) that indicates the putativevirulence gene located on the virulenceplasmid, pWT3 (of E. coli strain V-1). Theability of the organisms to kill chickenembryonated eggs has been used as a measureof virulence for the organisms tested. Whenelectroporated into the lab strain DH5α, pWT3did not bestow a stable ability to kill chickenembryos in the chicken embryo lethality assay.Analysis of data involving the weights ofembryos postinoculation has not been useful inthis study.Initially, an isolate was created that lackedthe plasmid pWT3 but was otherwise identicalto isolate V-1. Colicin plasmids can stablyintegrate into the chromosome and continue tofunction. This is the case with our V-1 mutant;the plasmid never reoccurred in the strain, butthe genes present on the plasmid were presentin the V-1 mutant genomic preparations.Clearly, some other knockout mutants willhave to be created in order to determine thecontribution of this plasmid to thepathogenesis of colibacillosis.Richard E. Wooley, Penelope S. Gibbs, andThomas P. Brown.rwooley@calc.vet.uga.edu12